1. Field of the Invention
The present invention relates to a waveguide type optical device consisting of an optical waveguide chip, light emitting and detecting semiconductor devices optically connected with the optical waveguide chip and a chip housing body for housing the optical waveguide chip and mounting the light emitting and detecting semiconductor devices. In particular, the present invention relates to the structure of the waveguide type optical device and a method for simply and optically mounting light emitting and detecting semiconductor devices on the chip housing body in high precision.
2. Description of the Related Art
Different from a bulk type optical device including discrete optical elements such as a prism and lens, a waveguide type optical device is composed of high integrated optical circuits Fabricated on an optical waveguide chip, which will be abbreviated as "waveguide chip" hereinafter, under a wafer process. The waveguide chip is effective in reducing the size of the optic device, and it is expected that by virtue of the waveguide chip, a small sized optical module will be produced in low costs so that the module will be widely applied to a subscriber communication network in a multimedia communication system for example.
As examples of the optical circuits fabricated on the waveguide chip, there are an optical waveguide circuit and an optical modulator. The optical waveguide circuit, which will be abbreviated "optical waveguide" or simply "waveguide" hereinafter, is provided by processing quartz glass formed on a silicon wafer, producing a Silica-Based optical waveguide. The optical modulator is provided by diffusing titanium (Ti) on a substrate made of lithium niobate (LiNbO.sub.3). In particular, the Silica-Based optical waveguide is suitable for the optical module in use. Because, the Silica-Based optical waveguide has a high matching property with an optical fiber used in a transmission line of the subscriber communication network. The optical waveguide used in the waveguide chip is designated to the Silica-Based optical waveguide hereinafter.
The light emitting or the light detecting semiconductor device or element is usually packed in a CD package used in a compact disc apparatus. Because, the CD package is easily fitted to the chip housing body. The optical semiconductor element is connected with the optical waveguide of the waveguide chip for converting an optical signal fed to the waveguide type optical device to an electrical signal or an electrical signal fed to the waveguide type optical device to an optical signal. Optical fibers of the transmission line or optical fibers connected with another waveguide type optical device are led to the waveguide type optical device for receiving or transmitting the optical signals at or from the waveguide type optical device. A connection point at which the optical fiber is connected with the optical waveguide in the waveguide chip will be called "port" hereinafter.
Two kinds of the optical semiconductor elements, a light detecting element and a light emitting element, are applied to the waveguide type optical device. A photo diode (PD) is a typical light detecting element, and a laser diode (LD) is a typical light emitting element. Therefore, the light detecting element will be called "PD element" and the light emitting element will be called "LD element" hereinafter, and a device which packs the PD element and an electrical circuit associated with the PD element will be called "PD assembly" and a device which packs the LD element and an electrical circuit associated with the LD element will be called "LD assembly" hereinafter.
FIGS. 1A and 1B illustrate schematic inside plan views of two typical waveguide type optical devices (WAVEGUIDE TYPE OPTICAL DEVICEs) (101 and 102) of the related art. The WAVEGUIDE TYPE OPTICAL DEVICE 101 or 102 includes a waveguide chip (11 or 12), a PD assembly (PD ASSEMBLY) (411 or 412), an LD assembly (LD ASSEMBLY) (412 or 422) and an optical fiber (31 or 32). The waveguide chip 11 or 12 is provided in a chip housing body (21 or 22), and the PD ASSEMBLY 411 Or 412 is fitted to the chip housing body 21 or 22 and the optical fiber 81 or 32 is placed anywhere close to the chip housing body 21 or 22.
The WAVEGUIDE TYPE OPTICAL DEVICEs 101 and 102 treat a multi-wave optical signal of for example two wavelengths .lambda..sub.1 such as 1.31 .mu.m and .lambda..sub.2 such as 1.55 .mu.m.
In FIG. 1A, WAVEGUIDE TYPE OPTICAL DEVICE 101 is for receiving an optical signal of wavelength .lambda..sub.1 which will be called "received optical signal of .lambda..sub.1 " hereinafter, and transmitting another optical signal of .lambda..sub.1 which will be called "transmitting optical signal of .lambda..sub.1 " hereinafter, and for interactively transferring an optical signal of wavelength .lambda..sub.2 through WAVEGUIDE TYPE OPTICAL DEVICE 101. The transferring optical signal of wavelength .lambda..sub.2 will be called "transferring optical signal of .lambda..sub.2 " hereinafter.
In FIG. 1B, WAVEGUIDE TYPE OPTICAL DEVICE 102 is for receiving received optical signals of .lambda..sub.1 and .lambda..sub.2 and transmitting optical signals of .lambda..sub.1 and .lambda..sub.2, respectively.
A waveguide (151) is fabricated on the waveguide chips 11 and 12, and in the waveguide chips 11 and 12, a wavelength-division-multiplexer (WDM) (111) is fabricated on the waveguide 151 on a transmission route of a multi-wave optical signal of wavelength .lambda..sub.1 and .lambda..sub.2, which will be called "multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 " hereinafter, and a Y type 3 dB coupler (121) is fabricated on the waveguide 151 on a transmission route of the received and transmitting optical signals of .lambda..sub.1. In the waveguide chip 12, another Y type 3 dB coupler (122) is fabricated on the waveguide 151 on a transmission route of the received and transmitting or the transferring optical signals of .lambda..sub.1. in FIG. 2B. The WDM 111 is for dividing a received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 into the received optical signal of .lambda..sub.1 and that of .lambda..sub.2 and multiplying the transmitting optical signal of .lambda..sub.1 and that of .lambda..sub.2 to a transmitting multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2.
In FIG. 1A, the received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 arrives at WAVEGUIDE TYPE OPTICAL DEVICE 101 through an optical fiber (31) of the transmission line. The optical fiber 31 is fixed to the chip housing body 21 with a bushing 301. The received multiplex optical signal of .lambda..sub.1 /.lambda..sub.2 is fed to WDM 111 through a port 131 at which the optical fiber 31 is optically connected with the waveguide 151. Then at WDM 111, the received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 is divided into the received optical signal of .lambda..sub.1 and that of .lambda..sub.2. After dividing, the received optical signal of .lambda..sub.1 is led to a PD assembly (PD ASSEMBLY) (411) through the Y type 3 dB coupler 121 and a waveguide terminal, not having a reference numeral, of the waveguide 151 and the received optical signal of .lambda..sub.2 is led to the optical fiber 32 through a port 132. The Y type 3 dB coupler 121 is for dividing the power of the received optical signal of .lambda..sub.1 half, so that the half power of the received optical signal of .lambda..sub.1 is sent to PD ASSEMBLY 411 and an LD assembly (LD ASSEMBLY) (412) respectively. Then the received optical signal (half power) of .lambda..sub.1 is detected and converted to a received electrical signal at LD ASSEMBLY 412 and the received electrical signal is output from LD ASSEMBLY 412 through an electric wire 4111. The other half power of the received optical signal of .lambda..sub.1 is sent to LD ASSEMBLY 412. However, LD ASSEMBLY 412 produces no output. Because, LD ASSEMBLY 412 has the function only for emitting an optical signal. The received optical signal of .lambda..sub.2 is led to the optical fiber 32, which is fixed to the chip housing body 21 with a bushing 302, through a port 132. Meanwhile, when a transmitting electrical signal is fed to LD ASSEMBLY 412 through an electric wire 4121, the transmitting electrical signal is converted to a transmitting optical signal of .lambda..sub.1 so that the transmitting optical signal of .lambda..sub.1 is emitted from LD ASSEMBLY 412. The transmitting optical signal of .lambda..sub.1 is fed to WDM 111 through another waveguide terminal, not having a reference numeral, of the waveguide 151 and the Y type 3 dB coupler 121. The power of the transmitting optical signal of .lambda..sub.1 arrived at the Y type 3 dB coupler 121 from LD ASSEMBLY 412 is almost sent to WDM 111. Because, by virtue of the power isolation property of the Y type 3 dB coupler, the power sent to PD ASSEMBLY 411 is almost 20 dB less than the power sent to WDM 111. In FIG. 1A, the transferring optical signal of .lambda..sub.2 fed to WAVEGUIDE TYPE OPTICAL DEVICE 101 through the optical fiber 32 fixed to the chip housing body 21 with a bushing 302 is sent to WDM 111 through the port 132 and the waveguide 151. At WDM 111, the transferring optical signal of .lambda..sub.2 arrived at WAVEGUIDE TYPE OPTICAL DEVICE 101 is multiplied with the transmitting optical signal of .lambda..sub.1 from LD ASSEMBLY 412, producing a transmitting multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2. The transmitting multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 produced at WDM 111 is transmitted from WAVEGUIDE TYPE OPTICAL DEVICE 101 through the optical fiber 31. The multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 transmitted from WAVEGUIDE TYPE OPTICAL DEVICE 101 will be called "transmitted multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 " hereinafter.
In FIG. 1B, the same as the description of the received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 in FIG. 1A, when the received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 arrives at WAVEGUIDE TYPE OPTICAL DEVICE 102 through the optical fiber 31, the received multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 is divided into the received optical signals of .lambda..sub.1 and .lambda..sub.2. After dividing, the same as described in FIG. 1A, the received optical signal of .lambda..sub.1 is led to PD ASSEMBLY 411 through the Y type 3 dB coupler 121 and a waveguide terminal not having a reference numeral. However, the received optical signal of .lambda..sub.2 is led to PD ASSEMBLY 421 through the Y type 3 dB coupler (122) having the same function as the Y type 3 dB coupler 121 and a waveguide terminal not having a reference numeral. Then the received optical signal of .lambda..sub.2 is detected and converted to another received electrical signal at PD ASSEMBLY 421 and the received electrical signal is output from PD ASSEMBLY 421 through an electric wire 4211. As described in reference with FIG. 1A, when the transmitting electrical signal is fed to LD ASSEMBLY 412 in FIG. 1B, the electrical signal is converted to the transmitting optical signal of .lambda..sub.1. The transmitting optical signal of .lambda..sub.1 is emitted from LD ASSEMBLY 412 and red to WDM 111 through a waveguide terminal not having reference numeral and the Y type 3 dB coupler 121. Meanwhile, another electronic signal fed to LD ASSEMBLY 422 is converted to a transmitting optical signal of .lambda..sub.2 and the transmitting optical signal of .lambda..sub.2 is sent to WDM 111 through a waveguide terminal not having a reference numeral and the Y type 3 dB coupler 122. As a result, the transmitting optical signal of .lambda..sub.1 sent from LD ASSEMBLY 412 and the transmitting optical signal of .lambda..sub.2 sent from LD ASSEMBLY 422 are multiplied to a transmitting multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 at WDM 111. The transmitting multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2 is transmitted from WAVEGUIDE TYPE OPTICAL DEVICE 102 to the transmission line through the optical fiber 31, as the transmitted multi-wave optical signal of .lambda..sub.1 /.lambda..sub.2.
In FIGS. 1A and 1B, the arrows depicted with .lambda..sub.1, .lambda..sub.2 and .lambda..sub.1 /.lambda..sub.2 show the transferring directions of the received, transmitted, transmitting or a transferring optical signals of .lambda..sub.1, .lambda..sub.2 and .lambda..sub.1 /.lambda..sub.2.
In the related art, the waveguide type optical device described in reference with FIG. 1A or 1B has the following problems. Generally, in the fabrication of the waveguide type optical device, delicate optical adjustment has been required to connect the optical fiber of the transmission line, the LD assembly, and the PD assembly respectively with the waveguide provided in the waveguide type optical device. A lot of skill has been required to the optical adjustment for the optical connection, so that in the fabrication of the waveguide type optical device, a large percentage of manhours has been wasted for the optical adjustment. In particular, in the process of installing the LD assembly to the waveguide type optical device, it takes a lot of time for the optical adjustment. Because, an optically emitting aperture of the LD element is so small as 1 to 2 .mu.m. Furthermore, the waveguide type optical device of the related art has the PD assembly and the LD assembly individually, so that the optical adjustment has to be performed individually. This results in wasting a lot of time for the optical adjustment to the PD element in the PD assembly and the LD element in the LD assembly. This causes a large manhours to the fabrication of the waveguide type optical device.
In FIG. 1A, the optical adjustment is required to be performed twice for PD ASSEMBLY 411 and LD ASSEMBLY 412, and in FIG. 1B, the optical adjustment is required to be performed four times for PD ASSEMBLY 411, LD ASSEMBLY 412, PD ASSEMBLY 421 and LD ASSEMBLY 422. Above all, it has taken a lot of time for the optical adjustment on LD ASSEMBLY 412 in FIGS. 1A and 1B and LD ASSEMBLY 422 in FIG. 1B. This has been the first problem of the waveguide type optical device in the related art.
In FIGS. 1A and 1B, even though the waveguide chips 11 and 12 are fabricated to a small size by the wafer process, PD ASSEMBLies 411 and 421 and LD ASSEMBLies 412 and 422 must be individually fitted to the chip housing bodies 21 and 22. As a result, it has been impossible to make the space for arranging WAVEGUIDE TYPE OPTICAL DEVICE 101 or 102 small. This has been the second problem of the waveguide type optical device in the related art.
As shown in FIG. 1A, the optical fibers 31 and 32 pass through two walls of the chip housing body 21, which are opposed to each other. Therefore, when the optical fibers 31 and 32 are bunched together close by WAVEGUIDE TYPE OPTICAL DEVICE 101, the space for making the optical fiber 31 or 32 pass a side of the chip housing body 21 is needed. Furthermore, since PD ASSEMBLY 411 and LD ASSEMBLY 412 are connected with the waveguide circuit lead out from the Y type 8 dB coupler 121 in FIG. 1A or 1B and PD ASSEMBLY 421 and LD ASSEMBLY 422 are connected with the waveguide circuit lead out from the Y type 3 dB coupler 122 in FIG. 1B, the PD ASSEMBLY 411 and LD ASSEMBLY 412 and the PD ASSEMBLY 421 and LD ASSEMBLY 422 are fitted to the walls, which are adjacent to each other, of the chip housing body 21 and the chip housing body 21, respectively. Therefore, when the electric wires connected with PD ASSEMBLY 411 and LD ASSEMBLY 412 are bunched together close by WAVEGUIDE TYPE OPTICAL DEVICEs 101 or 102 and when the electric wires connected with PD ASSEMBLY 421 and LD ASSEMBLY 422 are bunched together close by WAVEGUIDE TYPE OPTICAL DEVICEs 102, the space for making the electric wires pass the side of the chip housing body 21 or 22 is needed, respectively. As a result, though WAVEGUIDE TYPE OPTICAL DEVICE 101 (102) becomes small in size due to the adoption of the waveguide chip 11 (12) to WAVEGUIDE TYPE OPTICAL DEVICE 101 (102), large space has to be provided for WAVEGUIDE TYPE OPTICAL DEVICE 101 (102) in consideration of the place for arranging the optical fibers 31 and 32 and the electric wires around WAVEGUIDE TYPE OPTICAL DEVICE 101 (102). In particular, when many waveguide type optical devices are arranged close by each other, a lot of spaces for passing the optical fibers and the electric wires are required around the waveguide type optical devices, which results in requiring a large space for arranging the waveguide type optical devices. This has been the third problem of the waveguide type optical device in the related art.